WDXS31 PGTW 070300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 08S (BATSIRAI) 
WARNING NR 023//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 23.1S 42.2E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 123 NM EAST-SOUTHEAST OF EUROPA ISLAND
   MOVEMENT PAST 6 HOURS: WESTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 13 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A BROAD,
RAGGED ROTATION, WITH SCATTERED, UNORGANIZED CONVECTION PRIMARILY
TO THE SOUTH. A 062158Z AMSR2 37GHZ MICROWAVE IMAGE DEPICTED WEAK
LOW LEVEL BANDING ON THE NORTH SIDE OF THE THE CONVECTION, WRAPPING
INTO THE LOW LEVEL CIRCULATION CENTER (LLCC), AND LENT MEDIUM
CONFIDENCE TO THE INITIAL POSITION. ANIMATED SHORTWAVE INFRARED
IMAGERY SUGGESTS THAT THE LLCC MOVED OFFSHORE AROUND 061600Z, THEN
TRACK NEARLY DUE WEST OR A BIT NORTH OF DUE WEST, BUT BASED ON THE
MICROWAVE IMAGERY, APPEARS TO HAVE BECOME QUASI-STATIONARY NEAR THE
INITIAL POSITION. THE INITIAL INTENSITY OF 40 KNOTS IS ASSESSED
WITH MEDIUM CONFIDENCE, HEDGED HIGHER THAN A PGTW CURRENT INTENSITY
ESTIMATE OF T2.0 BASED ON A BROAD SWATH OF 35-40 KNOT WINDS IN THE
062158Z AMSR2 PASSIVE MICROWAVE WIND FIELD ANALYSIS. THE SYSTEM IS
DRIFTING RATHER AIMLESSLY AT THE MOMENT IN A WEAK STEERING PATTERN,
AS IT APPROACHES THE SUBTROPICAL RIDGE (STR) SHEAR IS LOW AND SSTS
ARE WARM, BUT OUTFLOW ALOFT IS SOMEWHAT LIMITED AND DRY AIR IS
WRAPPING INTO THE CORE FROM THE EAST AND SOUTH.

INITIAL WIND RADII BASIS: OTHER 

CURRENT STEERING MECHANISM: WEAK STEERING FLOW IN COL REGION AT
RIDGE AXIS

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   CIMSS ADT: 40 KTS AT 062345Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 0-5 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: MODERATE POLEWARD
   OTHER FACTORS: MID-LEVEL DRY AIR

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: MEDIUM

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: IN THE IMMEDIATE NEAR-TERM, TC 08S WILL
CONTINUE TO DRIFT SLOWLY AS IT REMAINS IN THE COL REGION ALONG THE
STR AXIS. GLOBAL MODELS ALL INDICATE THE RIDGE AXIS MOVING
NORTHWARD OVER THE NEXT 12 TO 24 HOURS, AND AS THIS OCCURS, TC 08S
WILL PROGRESSIVELY TAKE ON A MORE SOUTHWESTWARD TRACK. THE SYSTEM
WILL ROUND THE RIDGE AXIS NO LATER THAN TAU 24 AND BEGIN TO
ACCELERATE ONTO A SOUTHEASTWARD TRACK THROUGH THE REMAINDER OF THE
FORECAST PERIOD. AS THE SYSTEM MOVES FURTHER FROM LAND, IT WILL
MOVE AWAY FROM THE WEDGE OF DRY AIR CURRENTLY BEING PULLED OFFSHORE
AND INTO THE CORE OF THE SYSTEM, AND BECOME COCOONED IN SMALL
POCKET OF MOISTURE. THE ENVIRONMENT WILL BE CONDUCIVE FOR
INTENSIFICATION, WITH ENHANCED POLEWARD OUTFLOW, LOW SHEAR AND WARM
(27-28C) AND THE SYSTEM IS FORECAST TO PEAK OUT AT 50 KNOTS BY TAU
36. THEREAFTER, INCREASING SHEAR AND DRY AIR ENTRAINMENT WILL
INDUCE A WEAKENING TREND THROUGH THE REMAINDER OF THE FORECAST. THE
SYSTEM WILL BEGIN SUBTROPICAL TRANSITION BY TAU 48 AS IT STARTS TO
INTERACT WITH A MID-LATITUDE TROUGH RAPIDLY APPROACHING FROM THE
WEST, AND MOVES POLEWARD OF THE 26C ISOTHERM. THE SYSTEM IS
FORECAST TO COMPLETE TRANSITION TO A GALE-FORCE SUBTROPICAL LOW NO
LATER THAN TAU 72.  

MODEL DISCUSSION: TRACK GUIDANCE IS IN VERY GOOD AGREEMENT THROUGH
THE FORECAST PERIOD WITH A MINIMAL SPREAD OF ABOUT 100NM AT TAU 72.
HOWEVER IN LIGHT OF THE RATHER UNEXPECTED MOTION OVER THE PAST SIX
HOURS, THERE IS ONLY MEDIUM CONFIDENCE IN THE FORECAST TRACK AS THE
TRACK MOTION OVER THE NEXT 12 HOURS WILL HAVE A LARGE IMPACT ON THE
ULTIMATE TRACK DIRECTION AND SPEED. INTENSITY GUIDANCE IS IN GOOD
AGREEMENT THROUGH THE FORECAST PERIOD, AND SUPPORTS THE
INTENSIFICATION THROUGH TAU 36 FOLLOWED BY STEADY WEAKENING THROUGH
THE SUBTROPICAL TRANSITION. THE JTWC FORECAST LIES ABOUT FIVE KNOTS
ABOVE THE CONSENSUS MEAN THROUGH TAU 36 THEN TRACKS THE CONSENSUS
MEAN THEREAFTER WITH MEDIUM CONFIDENCE. 

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   INTENSITY 0 - 72 HR: MEDIUM//
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